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Stephan Renatus
04a3523b22
`contains` provides an alternative way to declare partial sets:
p contains x {
x := { "foo": "bar"
}
which is the same as
p[x] {
x := { "foo": "bar"
}
The keyword is enabled by importing `future.keywords.contains`, and
when it _is enabled_, the format will be used for all partial sets in
that file for pretty-printing.
`if` is a new keyword allowing for more readable rule definitions:
The syntax is
NAME [if] { EXPR [EXPR...] }
and the is a shorthand allows dropping the braces around the expression
if there is only one:
NAME if EXPR
For example, this allows expressions like
allow if not deny
f(xs) if every x in xs { x != "foo" }
The one exception here are partial sets: they cannot use `if` UNLESS
they use `contains`:
p[x] { x := "foo" } # valid
p contains x { x := "bar" } # valid
p contains x if { x := "bar" } # valid
p[x] if { x := "foo" } # invalid
This is because we want to interpret that differently (as an object
rule defining `p.foo = true`) in the near future.
The formatter works in the same way: if `future.keywords.if` is imported, it
will be used where it can be used.
We don't want to be too eager when it comes to introducing syntactic sugar.
So this will be rewritten, because head and body expression are on the same
line:
p := 5 if { time.day_of_week() == "Monday" }
# => p := 5 if time.day_of_week() == "Monday"
but this won't:
p := 5 if {
time.day_of_week() == "Monday"
}
The rationale here is that if the policy author decided that they want this on
an extra line, we won't mess with it.
This also sidesteps the need to check if both the head and the single body
expression have a comment.
This change includes various docs updates. Notable exceptions are the GK docs,
since it will take a while for these keywords to be come available there; and
the frontpage: merging a PR would update the frontpage immediately, and we
don't want to show something there that isn't available in the latest release.
Signed-off-by: Stephan Renatus <stephan.renatus@gmail.com>